1. Field of the Invention
The present invention relates to an image reading apparatus in which an image of a book document and so on is picked up, wherein an outline of a document and a distance to a document surface is detected, a size of the document and an offset amount from a reference position of placement are found and an appropriate image reading operation is executed.
2. Description of the Prior Art
Conventionally, regard to an image reading apparatus in which a document is read with face down, there has been known an apparatus wherein a size of the document is recognized by detecting a difference of a density between a back of a cover for holding the document and a document surface. Also, regard to an image reading apparatus in which a document is read with face up, there has been known an apparatus wherein, in the case of a book document or the like of which its surface exhibits a spacial curve, a height distance to the document surface is detected and, based on the detected, height distance, an image distortion is corrected. Similarly, there has been known an image reading apparatus wherein an edge of an upper end of a document surface with face up is picked up and, together with recognizing an outline by detecting a difference of brightness between the surface and a background focus detecting plate, a height of the document is detected, and, based on the detected height, the read image is corrected (for example, refer to Japanese Laid-Open Patent Publication No.60-254869). Also, according to a technique upon correcting an image distortion caused by reading an image of a curved document, there has been know an apparatus wherein linear light is emitted to a document surface at a specified angle, the projected image is picked up to detect a curvature of the document and in accordance with the curvature the read image is corrected.
However, according to the above-mentioned image reading apparatus in which the document is set with face down, in the case of using a document having a thickness such as a book document, since a cover for holding the document can not be closed, as the result, a problem occurs that a size of the document can not be detected. Also, according to the image reading apparatus in which the document is set with face up, if the read outline dimension of the document is used as the size of the document without correction, by influence of the height of the document, a problem occurs that it is measured larger than the actual size of the document. Furthermore, according to the image reading apparatus as stated above wherein a height of the document is obtained from a read image of the document, in cases in which the document is not placed correctly on a document table or the document has a large cover, when an edge of an upper end of a document surface is put apart from a reference position, accurate height data can not be given, so that a reproduced image quality may have defects. Also, in correcting an image distortion, if the degree of the image distortion exceeds a predetermined limit, since it can not be corrected appropriately, image pick up is not executed perfectly.
The present invention is made to solve the above-mentioned problems. An object of the present invention is to provide an image reading apparatus in which a document is optically scanned and image pickup is executed, and a document size is obtained by measuring an outline of a document and a distance (height) to the document, and then an appropriate selection of an optimum paper/magnification and erasing of an image of a portion irrelevant to the document can be achieved. Another object of the present invention is to provide an image reading apparatus in which detected data of height of the document is corrected or, an image pickup error is prevented by informing an operator that the document is not placed correctly, by detecting a document setting position (offset amount from a reference setting position) or judging whether or not a degree of an image distortion is within a correctable range.
In accomplishing the above-mentioned objects, according to the present invention, an image pickup device reads a document placed on a document table with scanning and a height detecting means detects a height of the document. An outline measuring means detects an edge portion of a document surface from the image read by the image pickup device and, based on detected result, an outline of the document is obtained. Based on data of the height of the document detected by the above-mentioned operation and data of the outline of the document measured by the outline measuring means, a calculating means calculates a document size. By selecting optimum paper/magnification and erasing a portion of an image irrelevant to the document in accordance with the calculated document size, it is able to pickup the image appropriately.
Further, according to the present invention, an image pickup device reads a document placed on a document table, a height detecting means detects a height of the document, and a document position recognizing means recognizes a position that the document is placed by the image data read by the image pickup device. In accordance with the recognized position of the document, a correcting means corrects detected data of the height of the document. By use of the corrected data of the height of the document, the read image is properly processed and, when the document is put apart from a reference position of placement over a predetermined value, it is possible to inform an operator that the document is not placed correctly or to stop an image pickup operation temporarily.
Furthermore, according to the present invention, an image pickup device reads a document placed on a document table with scanning, and an, image distortion detecting means detects a degree of an image distortion attributed to a configuration of the document. A correcting means corrects the image distortion read by the image pickup device in accordance with the detected degree of the image distortion, and a judging means judges whether or not the degree of the image distortion is within a correctable range. If the degree of the image distortion is not within the correctable range, it is possible to inform an operator that the document is not placed correctly or to stop an image pickup operation temporarily.
Still furthermore, according to the present invention, an image pickup device reads a document placed on a document table with scanning, and a detecting means detects an edge of an upper end of a document surface. A height calculating means calculates data of the height of the document based on an edge detecting result, a correcting means detects the minimum value from the obtained height data, and corrects an alteration of the document height owed to an offset amount from a document reference position, based on the minimum value. By processing the read image with use of the height data, an appropriate read image is obtained.